User terminal and radio communication method

ABSTRACT

For the purpose of properly controlling communication using a number of cells including cells that use different numerologies than existing LTE systems, a user terminal that communicates by using a number of cells including a first cell and a second cell has a receiving section that receives, from the first cell, information about synchronization between the first cell and the second cell and/or information about a configuration of a synchronization signal block in the second cell, and a control section that controls a processes for connecting with the second cell based on the information about synchronization and/or the information about the configuration of the synchronization signal block.

TECHNICAL FIELD

The present invention relates to a user terminal and a radiocommunication method in next-generation mobile communication systems.

BACKGROUND ART

In the UMTS (Universal Mobile Telecommunications System) network, thespecifications of long term evolution (LTE) have been drafted for thepurpose of further increasing high speed data rates, providing lowerlatency and so on (see non-patent literature 1). Also, thespecifications of LTE-A (also referred to as “LTE-advanced,” “LTE Rel.10,” “LTE Rel. 11,” “LTE Rel. 12” or “LTE Rel. 13”) have been draftedfor further broadbandization and increased speed beyond LTE (alsoreferred to as “LTE Rel. 8” or “LTE Rel. 9”), and successor systems ofLTE (also referred to as, for example, “FRA (Future Radio Access),” “5G(5th generation mobile communication system),” “NR (New Radio),” “NX(New radio access),” “FX (Future generation radio access),” “LTE Rel.14,” “LTE Rel. 15” or later versions) are under study.

In LTE Rel. 10/11, carrier aggregation (CA) to integrate multiplecomponent carriers (CC) is introduced in order to achievebroadbandization. Each CC is configured with the system bandwidth of LTERel. 8 as 1 unit. In addition, in CA, multiple CCs under the same radiobase station (eNB (eNodeB)) are configured in a user terminal (UE (UserEquipment)).

Meanwhile, in LTE Rel. 12, dual connectivity (DC), in which multiplecell groups (CGs) formed with different radio base stations areconfigured in a UE, is also introduced. Each cell group is comprised ofat least 1 cell (or CC). In DC, since multiple CCs of different radiobase stations are integrated, DC is also referred to as “inter-eNB CA.”

Also, in existing LTE systems (for example, LTE Rel. 8 to 13),synchronization signals (PSS/SSS), broadcast channel (PBCH) and so onwhich a user terminal uses in initial access procedures are allocated,on a fixed basis, in fields that are determined in advance. By detectingthe synchronization signals in cell search, the user terminal canestablish synchronization with the network, and, furthermore, identifythe cell (for example, cell ID) at which the user terminal shouldconnect with. Furthermore, the user terminal can acquire systeminformation by receiving the broadcast channel (PBCH and SIB) after thecell search.

CITATION LIST Non-Patent Literature

-   Non-Patent Literature 1: 3GPP TS 36.300 “Evolved Universal    Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial    Radio Access Network (E-UTRAN); Overall Description; Stage 2”

SUMMARY OF INVENTION Technical Problem

Future radio communication systems (for example, 5G, NR, etc.) areexpected to realize various radio communication services so as tofulfill mutually varying requirements (for example, ultra high speed,large capacity, ultra-low latency, etc.). For example, regarding 5G/NR,studies are in progress to provide radio communication services,referred to as “eMBB (enhanced Mobile Broad Band),” “IoT (Internet ofThings),” “mMTC (massive Machine Type Communication),” “M2M (Machine ToMachine),” and “URLLC (Ultra Reliable and Low Latency Communications).”

In addition, 5G/NR is expected to support flexible use of numerologiesand frequencies, and realize dynamic frame configurations. Here,“numerology” refers to communication parameters in the frequencydirection and/or the time direction (for example, at least one of thesubcarrier spacing (subcarrier interval), the bandwidth, the symbolduration, the time duration of CPs (CP duration), the subframe duration,the time duration of TTIs (TTI duration), the number of symbols per TTI,the radio frame configuration, the filtering process, the windowingprocess, and so on).

When cells that use different numerologies than existing LTE systems(also referred to as “NR/5G-cell”) are supported, it is likely that auser terminal communicates by using a number of cells including theseNR/5G-cells (for example, by using CA and/or DC). However, how tocontrol communication using multiple cells including NR/5G-cells is notdecided.

The present invention has been made in view of the above, and it istherefore an object of the present invention to provide a user terminaland a radio communication method, whereby communication to use a numberof cells, including cells that use different numerologies than existingLTE systems, can be controlled properly.

Solution to Problem

According to one aspect of the present invention, a user terminal has areceiving section that receives, from the first cell, information aboutsynchronization between the first cell and the second cell and/orinformation about a configuration of a synchronization signal block inthe second cell, and a control section that controls a processes forconnecting with the second cell based on the information aboutsynchronization and/or the information about the configuration of thesynchronization signal block.

Advantageous Effects of Invention

According to the present invention, communication to use a number ofcells, including cells that use different numerologies than existing LTEsystems, can be controlled properly.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are diagrams to explain the concepts of CA and DC;

FIG. 2 is a diagram to explain the concept of SS blocks;

FIG. 3 is a diagram to show an example of an SS block transmissionmethod for use during single-beam operation;

FIG. 4 is a diagram to show an example of an SS block transmissionmethod for use during multi-beam operation;

FIG. 5 is a diagram to explain a method of controlling communicationbased on synchronization information between a number of cells;

FIGS. 6A to 6D are diagrams to explain methods of controllingcommunication based on synchronization information between a number ofcells and whether or not PBCH is configured;

FIGS. 7A to 7D are diagrams to show examples of SS block configurationsbased on whether or not PBCH is configured;

FIG. 8 is a diagram to show other examples of SS block configurationsbased on whether or not PBCH is configured;

FIG. 9 is a diagram to show an exemplary schematic structure of a radiocommunication system according to one embodiment of the presentinvention;

FIG. 10 is a diagram to show an exemplary overall structure of a radiobase station according to one embodiment of the present invention;

FIG. 11 is a diagram to show an exemplary functional structure of aradio base station according to one embodiment of the present invention;

FIG. 12 is a diagram to show an exemplary overall structure of a userterminal according to one embodiment of the present invention;

FIG. 13 is a diagram to show an exemplary functional structure of a userterminal according to one embodiment of the present invention; and

FIG. 14 is a diagram to show an exemplary hardware structure of a radiobase station and a user terminal according to one embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

In existing LTE systems, carrier aggregation (CA) and dual connectivity(DC) are supported as communication methods to use a number of cells (orCCs).

FIG. 1A shows communication between radio base stations and a userterminal when CA is used. In the example shown in FIG. 1A, radio basestation eNB 1 may be a radio base station to form a macro cell(hereinafter referred to as “macro base station”), and radio basestation eNB 2 may be a radio base station to form a small cell(hereinafter referred to as “small base station”). For example, a smallbase station may be structured as an RRH (remote radio head) thatconnects with a macro base station.

When CA is used, 1 scheduler (for example, a scheduler provided in macrobase station eNB 1) controls the scheduling of multiple cells. In adesign in which the scheduler provided in macro base station eNB 1controls the scheduling of a number of cells, for example, each radiobase station can be connected using an ideal backhaul, which is, forexample, a high-speed channel such as optical fiber.

FIG. 1B shows communication between radio base stations and a userterminal when DC is used. When DC is used, a design may be employed, inwhich a number of schedulers are provided independently, and theseschedulers each control the scheduling of one or more correspondingcells. To be more specific, the scheduler provided in the master basestation (MeNB (master eNB)) schedules the CCs belonging to the mastercell group (MCG). To be more specific, the scheduler provided in asecondary base station (SeNB (Secondary eNB)) schedules the CCsbelonging to a secondary cell group (SCG).

In a design in which the scheduler provided in a master base stationMeNB and the scheduler provided in a secondary base station SeNB eachcontrol the scheduling of one or more corresponding cells, for example,these radio base stations may be connected using non-ideal backhaul suchas the X2 interface. Therefore, DC enables 2 patterns of operations thatmight apply to the case where the master base station MeNB and thesecondary base station SeNB are synchronized for a certain level ofreliability (synchronous operation), and the case where no suchsynchronization is assumed (asynchronous operation).

Also, in an SCG, a PSCell (Primary Secondary Cell), which has functionsequivalent to those of a primary cell (PCell), such as a common searchspace, a PUCCH, being seen as always activated and so on, is configured.

Future radio communication systems are also expected to supportstand-alone (SA) communication, in which a newly-introduced carrier(also referred to as an “NR carrier” or an “NR cell”) can run alone,and, in addition, to support communication (CA and/or DC) to use anumber of cells, including at least an NR carrier. For example, DC maybe implemented by configuring radio base stations (LTE-eNBs) thatsupport existing LTE systems in an MCG, and configuring radio basestations (NR-gNBs) that support NR/5G in an SCG.

To be more specific, cells that support existing LTE system (LTE cells)constitute an MCG, and cells that support NR/5G (NR cell) constitute anSCG. The network (for example, a radio base station) reports systeminformation from an MCG cell (for example, PCell) to a user terminal.The user terminal receives system information (broadcast information)that is necessary for downlink communication, in, for example, the MIB(Master Information Block), which is transmitted in the broadcastchannel (PBCH), and the like.

In the PBCH (MIB), information that is necessary to receive the downlink(downlink bandwidth, downlink control channel format, system framenumber (SFN), etc.) is set forth in predetermined bits. The userterminal controls receipt of SIBs (System Information Blocks), which arecommunicated in the downlink shared data channel (PDSCH), based on theLTE-PBCH. By receiving SIBs, the user terminal can acquire minimumsystem information that is necessary to make communication.

Meanwhile, when the user terminal communicates with an SCG cell thatsupports NR/5G, the user terminal needs to acquire the radio frametiming and the system frame number (SFN) of the SCG. Therefore, the userterminal might acquire the SCG's radio frame timing and SFN by usingsignals transmitted from NR cells included in the SCG (for example,PSCell). For example, the user terminal acquires the radio frame timing(establishes synchronization) by using a synchronization signal (NR-SS)transmitted from an NR cell, and, furthermore, acquires the SFN by usinga broadcast channel (NR-PBCH). This allows, even when an LTE-eNB (MCG)and an NR-gNB (SCG) operate asynchronously, the user terminal tosynchronize with an NR cell (PSCell) that is included in the SCG, andidentify the SFN.

<SS Blocks>

Furthermore, 5G/NR are under study to define a resource unit that atleast contains synchronization signals (for example, NR-PSS and/orNR-SSS (hereinafter also referred to as “NR-PSS/SSS”)) as an “SS block,”and to communicate by using these SS blocks. An SS block(synchronization signal block) may be configured to contain a broadcastchannel (for example, NR-PBCH). In this case, the location of the SSblock and/or the number of prospective SS blocks may be defined in thespecification, on a fixed basis, per predetermined frequency band, sothat, when the user terminal detects an SS block, the user terminal candetermine at least one of the slot, subframe and radio frame timingsbased on this SS block (such as time index information corresponding tothe SS block).

Also, in 5G/NR, studies on single-beam or multi-beam operation areunderway. For example, during multi-beam operation, it may be possibleto repeat transmitting a whole SS burst set, which is comprised ofmultiple SS blocks, on a regular basis.

Now, SS blocks will be described below with reference to FIG. 2. FIG. 2is a diagram to explain the concept of SS blocks. An SS block, asillustrated in FIG. 2, at least contains a PSS (NR-PSS), SSS (NR-SSS)and PBCH (NR-PBCH). Note that synchronization signals other than the PSSand SSS (for example, a TSS (Tertiary SS)) may be included in SS blocks.

The user terminal detects the NR-PSS/SSS/PBCH corresponding to the sameSS block index. The PSS, SSS and PBCH that correspond to the same SSblock index are associated with each other. For example, the userterminal may assume that the PSS, SSS and PBCH that correspond to thesame SS block index are transmitted in the same beam. Note that the PSS,the SSS and the PBCH in the following description may be understood asmeaning the PSS for NR (NR-PSS), the SSS for NR (NR-SSS) and the PBCHfor NR (NR-PBCH), respectively.

A set of one or multiple SS blocks may be referred to as an “SS burst.”FIG. 2 shows an example of SS burst length=L. In this example, an SSburst is comprised of L SS blocks (SS block indices #0 to #L-1) that arecontiguous in time, but this is by no means limiting. An SS burst may beformed with SS blocks in which the frequency and/or time resources arecontiguous, or may be formed with SS blocks in which the frequencyand/or time resources are non-contiguous.

It is preferable that SS bursts are transmitted in a predetermined cycle(which may be referred to as “SS burst cycle”). Alternatively, SS burstsmay not be transmitted on a regular basis (and may be transmittedaperiodically). Also, one or more SS bursts may be referred to as an “SSburst set (SS burst series).” For example, a base station and/or a UEmay apply beam sweeping to the PSS/SSS/PBCH by using one or more SSbursts included in 1 SS burst set, and transmit these signals. Note thatSS burst sets are transmitted periodically. The UE may control receivingprocesses on assumption that SS burst sets are transmitted periodically(in an SS burst set cycle).

The PSS and the SSS, or the PSS (SSS) and the PBCH may betime-division-multiplexed (TDM (Time Division Multiplexing)) orfrequency-division-multiplexed (FDM (Frequency Division Multiplexing)).

A design may be employed here, in which prospective SS block locationsare specified, by the specification, on a per frequency band basis, sothat the user terminal can identify the index of an SS block based onsignals from inside the SS block. This allows the user terminal toidentify an SS block index from one or more signals in the SS block. Forexample, when the base station places an SS block index in an NR-PBCHand transmits this to the user terminal, the UE can acquire the SS blockindex from the PBCH upon receipt. Then, the user terminal can identifythe time index (the symbol number, the slot number, etc.) correspondingto the SS block index that is acquired.

FIG. 3 shows an example of SS block configuration in the eventsingle-beam operation is employed. FIG. 3 shows a case where an SS burstset supports n (for example, n=8) SS blocks (SS blocks #0 to #n-1), andthe cycle of SS burst sets is configured to a predetermined value (forexample, 20 ms). The radio base station transmits a PSS/SSS/PBCH in apredetermined SS block (here, SS block #0). When the user terminaldetects the PSS/SSS/PBCH corresponding to SS block #0, the user terminalcan identify the time index that is defined in association with SS block#0 (for example, the first slot of a subframe). Also, resources forother SS blocks (here, SS blocks #1 to #n) may be used to allocate othersignals such as data.

FIG. 4 shows an example of SS block configuration in the eventmulti-beam operation is employed. FIG. 4 shows a case where an SS burstset supports m SS blocks (SS blocks #0 to #m-1), and the cycle of SSburst sets is configured to a predetermined value (for example, 20 ms).The radio base station transmits PSS/SSS/PBCH, corresponding to a numberof predetermined SS blocks (here, SS blocks #0 to #5), respectively. Inthis case, the radio base station can apply different beams (here, 6types of beams) to the SS blocks and transmit each SS block.

Note that the beam corresponding to each SS block may be a transmittingbeam (Tx beam), or may be a pair of a transmitting beam and a receivingbeam (Rx beam). A pair of a transmitting beam and a receiving beam maybe referred to as a “beam pair link (BPL).”

When the user terminal detects the PSS/SSS/PBCH corresponding to apredetermined SS block (herein, SS block #3), the user terminal canidentify the time index that is defined in association with thispredetermined SS block #3. Also, resources for other SS blocks (here, SSblocks #6 to #m) may be used to allocate other signals such as data.

In this way, prospective SS block locations are defined in advance inassociation with time resources and/or the like, so that when the userterminal finds out an SS block index, the user terminal can alsoidentify the symbol index and/or the slot index. Also, by definingprospective SS block locations in advance, the number of bits requiredto report SS block indices can be reduced.

Now, in the above-described communication (for example, DC) to use anLTE-eNB (MCG) and an NR-gNB (SCG), communication might be controlledbased on synchronous operation. In this case, assuming that the radioframe is common (10 ms) between existing LTE and NR, the user terminalcan identify SFNs without receiving broadcast channels (for example,NR-PBCH) transmitted from NR cells (for example, PSCell).

So, the present inventors have a focused on the point that, whencommunication to involve multiple cells is carried out, the processesfor connecting with certain cells can be simplified depending on whatmode of operation applies between these multiple cells (for example,synchronous operation), and the present inventors have come up with theidea of reporting information about the synchronization between thesemultiple cells to a user terminal, and controlling the processes forconnecting with certain cells.

Also, the present inventors have come up with the idea of reportingassist information to a user terminal so as to allow the user terminalto identify the time indices pertaining to predetermined cells in unitsof symbols and/or slots.

Now, embodiments of the present invention will be described in detailbelow with reference to the accompanying drawings. Note that the radiocommunication methods according to the herein-contained embodiments maybe used individually or may be used in combination. Also, although caseswill be illustrated with the following description where dualconnectivity (DC) is employed as the mode of communication to use anumber of cells, this is by no means limiting. The present embodimentcan be applied to communication using multiple cells.

FIRST EXAMPLE

With a first example of the present invention, a case will be describedin which, when a user terminal communicates by using a number of cells,including at least a first cell and a second cell, information about thesynchronization between the first cell and the second cell is reported(see FIG. 5). Here, a case will be shown in which the first cell is aPCell and the second cell is a PSCell. Also, the cell group (MCG) toinclude the first cell is comprised of cells that support existing LTEsystems or cells that support 5G/NR. Also, the cell group (SCG) toinclude the second cell is comprised of cells that support 5G/NR.Obviously, the number of cell groups, the cells that constitute cellgroups and the like are by no means limited to these. In each cellgroup, one or more secondary cells may be included.

The network (for example, a radio base station) reports informationabout the synchronization (synchronization information) between thefirst cell and the second cell from the first cell to the user terminal.For example, when the radio base station (MeNB) reports systeminformation by using higher layer signaling (for example, dedicated RRCsignaling) in the first cell, the radio base station may reportinformation about the synchronization between the first cell and othercells (here, the second cell) together.

Based on the synchronization information reported in the first cell, theuser terminal determines whether or not synchronization is establishedbetween the first cell and the second cell, and controls the processesfor connecting with the second cell. The connection processes includethe process for receiving synchronization signals and/or broadcastsignals (for example, SS blocks) and the like.

The synchronization information may be information that explicitlyreports whether or not multiple cells are synchronized, or may beinformation that reports information about timing offsets (for example,SFN offsets). For example, the radio base station may report, to theuser terminal, whether or not the SFN offset between the first cell andthe second cell is less than a predetermined value (for example, lessthan 1), as synchronization information.

<Synchronous Operation>

If it is reported that varying cells are synchronized, the user terminaljudges that the SFN is the same (for example, the SFN offset is lessthan 1) between these varying cells. Alternatively, the user terminalmay judge that these varying cells operate synchronously when the SFNoffset between these varying cells is less than a predetermined value,or judge that these varying cells operate asynchronously when the SFNoffset is equal to or greater than the predetermined value.

The user terminal switches and controls at least part of the processesfor connecting with the second cell based on synchronization informationreported from the first cell. For example, if it is reported that thesecond cell is synchronized with the first cell, the user terminal mayassume that the SFN of the second cell is the same as that of the firstcell (for example, the SFN offset is less than 1), and exert control sothat broadcast channel (for example, NR-PBCH) detection does not takeplace in the second cell. Thus, the NR-PBCH detection process in theuser terminal can be skipped, and the receiving processes can besimplified.

Also, if it is reported that the second cell is synchronized with thefirst cell, the user terminal may assume that no broadcast channel (forexample, NR-PBCH) is transmitted in the second cell. In this case, theuser terminal may perform receiving processes on assumption that noNR-PBCH is contained in SS blocks.

Alternatively, synchronization information that indicates whether or notthe second cell is synchronized with the first cell, and informationabout the configuration of a predetermined channel/signal (for example,NR-PBCH) in the second cell may be reported separately to the userterminal (see FIG. 6). For example, when the second cell (NR cell) worksin non-stand-alone operation, the radio base station (MeNB) reports, tothe user terminal, that no NR-PBCH is configured in the second cell (seeFIG. 6B). In this case, the radio base station (SeNB) may transmit SSblocks not including the NR-PBCH. The user terminal may performreceiving processes on assumption that no NR-PBCH is contained in SSblocks.

If it is reported that no NR-PBCH is configured (or the user terminaljudges that no NR-PBCH is detected), the user terminal may assume thatthe reference signal (for example, NR-PBCH DMRS) used to demodulate theNR-PBCH is not configured (transmitted) either, and perform receivingprocesses accordingly. In this case, the user terminal may exert controlso that rate matching (for example, rate matching upon receipt of data(PDSCH)) is not performed for the NR-PBCH resource and/or the NR-PBCHDMRS resource. By this means, it is possible to reduce the load ofreceiving processes in the user terminal. On the other hand, when it isreported that the NR-PBCH is configured, the user terminal may exertcontrol so that rate matching is always performed for the NR-PBCHresource and/or the NR-PBCH DMRS resource.

Also, the radio base station may report whether or not the DMRS for theNR-PBCH is configured, apart from whether or not the NR-PBCH isconfigured. When the DMRS for the NR-PBCH is configured, the userterminal may perform receiving processes (for example, rate matching) onassumption that the DMRS for the NR-PBCH is transmitted, even if it isreported that the NR-PBCH is not configured. Alternatively, the userterminal may perform receiving processes on assumption that the DMRS forthe NR-PBCH is always transmitted, regardless of whether or not the DMRSfor the NR-PBCH is configured and/or whether or not the NR-PBCH isconfigured.

For example, when the second cell (NR cell) works in non-stand-aloneoperation, it is reported to the user terminal that the NR-PBCH isconfigured in the second cell (see FIG. 6A). In this case, the radiobase station (SeNB) places the NR-PBCH in SS blocks and transmits thesefor user terminals that directly connect to the second cell. A userterminal to connect to the first cell and the second cell can connect tothe second cell based on information (for example, synchronizationinformation) reported from the first cell, and therefore may becontrolled not to detect the NR-PBCH (that is, skip PBCH detection)transmitted in the second cell. In this case, the NR-PBCH detectionprocess in the user terminal can be skipped, and the receiving processescan be simplified.

FIG. 7 show cases in which a user terminal is reported that no NR-PBCHis configured (or the user terminal judges that no NR-PBCH is detected),and performs receiving processes, in the second cell, based on theassumption of SS block configurations in which no NR-PBCH is configured.The left half of FIG. 7 shows SS block configurations for when NR-PBCHsare configured, and the right half of FIG. 7 shows SS blockconfigurations for when NR-PBCHs are not configured. Also, FIGS. 7A to7D show cases where the PSS, SSS and PBCH are all allocated in SS blockconfigurations based on varying methods.

In FIG. 7A, when an NR-PBCH is configured, the PSS, the SSS and the PBCHare all allocated in different time units (subframes, slots, etc.). Whenno NR-PBCH is configured (or no NR-PBCH is detected), the user terminalperforms receiving processes (for example, detection) with respect tothe PSS and the SSS, and does not perform receiving processes for thePBCH.

FIG. 7B shows a case where, when an NR-PBCH is configured, the PSS andthe SSS, which are allocated contiguously, are allocated by beingsandwiched by a number of PBCHs. FIG. 7C shows a case where, when anNR-PBCH is configured, the PBCH is allocated between the PSS and an SSS.FIG. 7D shows a case where, when an NR-PBCH is configured, the PSS andthe SSS are allocated contiguously, and, furthermore, a number ofNR-PBCHs are allocated contiguously. When no NR-PBCH is configured (orno NR-PBCH is detected), the user terminal performs receiving processeswith respect to the PSS and the SSS, even in FIGS. 7B to 7D, and doesnot perform receiving processes for the PBCH.

When no NR-PBCH is configured in the second cell, other signals (forexample, data) may be allocated to the NR-PBCH field in SS blocks wherethe NR-PBCH would have been configured. This makes it possible toimprove the efficiency of the use of radio resources when the NR-PBCH isnot configured.

FIG. 7 show cases in which, even when no NR-PBCH is configured, SSblocks in which NR-PBCHs are configured are re-used (and in which, forexample, the NR-PSS/SSS are allocated in the same locations), but theseSS block configurations are by no means limiting. SS blockconfigurations for when NR-PBCHs are configured, and SS blockconfigurations for when NR-PBCHs are not configured may be defined both.In this case, SS block configurations for when NR-PBCHs are configured,and SS block configurations for when NR-PBCHs are not configured may bedefined in the specification in advance (see FIG. 8), per frequencyband.

The left half of FIG. 8 shows SS block configurations for when NR-PBCHsare configured, and the right half of FIG. 8 shows SS blockconfigurations for when NR-PBCHs are not configured. In SS blockconfigurations in which no NR-PBCH is configured, the allocation of theNR-PSS/SSS is defined without considering the location to allocate theNR-PBCH. Also, in SS block configurations in which no NR-PBCH isconfigured, different signals from the NR-PSS/SSS (for example, TSS) maybe defined.

<Asynchronous Operation>

When it is reported that varying cells are not synchronized, or when noreport is received to the effect that varying cells are synchronized,the user terminal determines that the SFN is different (for example, theSFN offset is 1 or more) between these varying cells, and controls theprocesses for connecting with the second cell.

When the NR-PBCH is configured in the second cell, the user terminal candetect the NR-PBCH and identify the timing of the second cell (forexample, the SFN, information pertaining to part of the SFN, etc.) (seeFIG. 6C). Information as to whether or not the NR-PBCH is configured maybe reported from the radio base station (MeNB) to the user terminal.

Also, even when the first cell and the second cell operateasynchronously, if the radio base station (for example, MeNB) knowsabout the SFN offset between the first cell and the second cell,information about this SFN offset may be reported to the user terminal.The user terminal can identify the SFN of the second cell based on theSFN of the first cell and the information about the SFN offset.

Also, when no NR-PBCH is configured in the second cell, the radio basestation (MeNB) may report the information about the SFN offset to theuser terminal (see FIG. 6D). The user terminal can identify the SFN ofthe second cell based on the SFN of the first cell and the informationabout the SFN offset. Furthermore, the user terminal may performreceiving processes based on the assumption of SS block configurationsin which no NR-PBCH is configured in the second cell.

In this way, the processes for connecting with a predetermined cell arecontrolled by reporting information about the synchronization between anumber cells to a user terminal, so that it is possible to simplify thereceiving processes and the like in the user terminal (in particular,during synchronous operation).

SECOND EXAMPLE

In a second example of the present invention, a case will be describedwhere information (also referred to as “assist information”) that allowsthe user terminal to find the time index on a per symbol basis and/or ona per slot basis in the second cell is reported from the first cell tothe user terminal (see FIG. 5). In the following description, cases willbe explained in which the second cell is a 5G/NR cell to use at leastbeamforming (BF). Obviously, this cell configuration is by no meanslimiting.

The network (for example, radio base station (MeNB)) reports assistinformation for allowing the user terminal to acquire the time index inthe second cell (PSCell), from the first cell to the user terminal. Theradio base station (MeNB) may report at least one of system information,synchronization information, and information about the configuration ofthe NR-PBCH and assist information to the user terminal together.

The assist information may be information about SS blocks transmitted inthe second cell. The information about SS block includes at least one ofinformation about the indices of SS blocks transmitted in the secondcell, the number of SS blocks transmitted in the second cell,information as to whether or not a signal for acquiring SS block indicesis available, and information about the range of SS block indices. Notethat the SS blocks transmitted in the second cell may be associated withgiven beams (or BPLs, radio resources, etc.), and the SS blocks may bereplaced by beams (or BPLs, radio resources, etc.). Alternatively, theassist information may be information about the beam operation(single-beam operation or multi-beam operation) in the second cell.

The radio base station (MeNB) may transmit predetermined assistinformation according to the mode of transmission (single-beam operationor multi-beam operation) that is employed in the second cell. In thefollowing, the assist information to be reported to the user terminalduring single-beam operation and the assist information to be reportedto the user terminal during multi-beam operation will be described.

<Single-Beam Operation>

When the second cell works in single-beam operation, the radio basestation (for example, MeNB) reports predetermined SS block indexinformation transmitted in the second cell to the user terminal, byhigher layer signaling and so on. The predetermined SS block indexinformation may be reported to the user terminal simultaneously (forexample, may be included in the same information element) with one ofsystem information, synchronization information, and NR-PBCHconfiguration information. Also, predetermined SS block indices may bedefined in association with predetermined time indices (for example,predetermined symbols and/or predetermined slots).

The user terminal can identify the predetermined time index (forexample, a predetermined symbol and/or predetermined slot) correspondingto an SS block by detecting the synchronization signal (for example,NR-PSS/SSS) included in the SS block. In this way, predetermined SSblock indices are defined in association with predetermined timeindices, so that, when an SS block index is detected, the user terminalcan determine at which timing in the radio frame this SS block wastransmitted. In this case, the user terminal can identify the time indexin the second cell without detecting the NR-PBCH.

<Multi-Beam Operation>

When the second cell works in multi-beam operation, the radio basestation (for example, MeNB) may report information as to whether or notthe signal for acquiring SS block indices (or beam indices) transmittedin the second cell is available and/or information about the range of SSblock indices to the user terminal, by way of higher layer signaling andso on. When the signal for acquiring SS block indices is transmitted inthe second cell, the user terminal detects the SS block index-acquiringsignal, in addition to the NR-PSS/SSS transmitted from the second cell(for example, NR cell), and finds the time indices.

Note that the information as to whether or not the signal for acquiringSS block indices is available does not have to be reported. Also, theuser terminal may perform receiving processes on assumption that SSblock index-acquiring signals are transmitted when multi-beam operationis employed.

Other block synchronization signals (TSS) different from NR-PSS/SSS maybe used as the SS block index-acquiring signal. In this case, byassociating the TSS sequence pattern with the SS block index, the userterminal can identify the SS block index (time index corresponding tothe SS block index) based on the detected TSS. In this way, by using TSSinstead of NR-PBCH including information such as SFN, the signaloverhead can be reduced and reliable detection is enabled by 1transmission.

Alternatively, as for the SS block index-acquiring signal, a PBCH thatis different in configuration (second NR-PBCH) from the NR-PBCHtransmitted (first NR-PBCH) may be used when the second cell works instand-alone operation or the like. For example, information (bits) to beincluded in the second NR-PBCH is made smaller than that in the firstNR-PBCH. For example, the second NR-PBCH may be designed to include onlySS block indices. In this way, by using the second NR-PBCH, the codingrate and the amount of resources can be reduced, so that the overheadcan be reduced and reliable detection is enabled by 1 transmission. Notethat an SS block may be comprised of an NR-PSS/SSS and a second NR-PBCH.

Also, when the second cell works in asynchronous/non-stand-aloneoperation, a second NR-PBCH that is designed differently from the firstNR-PBCH transmitted when the second cell works in stand-alone operationmay be used. In this case, information about the SS block index and theSFN (or at least part of the SFN) may be included in the second NR-PBCHand reported to the user terminal. Alternatively, the NR-PBCH includinginformation about the SFN (or at least part of the SFN) and the TSSassociated with the predetermined SS block index may be reported to theuser terminal.

<Reporting of Assist Information and User Terminal Operation>

Both single-beam operation and multi-beam operation may be supported inthe second cell. In this case, the radio base station (for example, theMeNB) may report, as assist information, at least one of informationabout beam operation (example 1), information about the number of beamsand beam indices (or the number of SS blocks and SS block indices)(example 2), information about on/off of each beam (example 3), andinformation as to whether or not symbol synchronization is established(example 4). The user terminal operation in each example will bedescribed below. Note that information about the synchronization betweenthe first cell and the second cell is reported from the radio basestation to the user terminal, apart from the assist information, or withthe assist information. Also, in the following example, it is preferableto use it when the first cell and the second cell work in synchronousoperation.

EXAMPLE 1

The radio base station (MeNB) reports beam operation-related information(for example, 1 bit) indicating whether the beam operation in the secondcell is single-beam operation or multi-beam operation, to the userterminal. In this case, the SS block index (for example, beam index)transmitted in the second cell may be configured on a fixed basis.

If it is reported that the second cell works in single-beam operation,the user terminal assumes that synchronization signals (for example,NR-PSS/SSS) to be detected in the second cell correspond topredetermined SS block indices. Then, the user terminal finds the timeindices, on a per symbol basis and/or on a per slot basis, based on thetime indices (symbols and/or slots) corresponding to the predeterminedSS block indices.

If it is reported that the second cell works in multi-beam operation,the user terminal performs receiving processes on the assumption ofpredetermined SS block configurations. Also, the user terminal mayperform receiving processes on assumption that SS block index-acquiringsignals are transmitted. The user terminal can identify a predeterminedSS block index based on a predetermined synchronization signal (forexample, NR-PSS/SSS) that is detected, and an SS block index-acquiringsignal (for example, a TSS and/or a second NR-PBCH). Each SS block maybe comprised of an NR-PSS/SSS and a SS block index-acquiring signal.

EXAMPLE 2

The radio base station reports the number of beams (or the number of SSblocks) transmitted in the second cell and active beam indices (or SSblock indices) to the user terminal. For example, in the event ofsingle-beam operation, it is reported to the user terminal that there is1 beam, and, in the event of multi-beam operation, it is reported to theuser terminal that there are multiple (two or more) beams. Also, inaddition to the number of beams, the beam index information for use fortransmitting SS blocks is reported to the user terminal.

If the second cell works in single-beam operation, for example, theradio base station reports the assist information to the user terminalto the effect that the number of beams is 1 and that the active beam isbeam index # X. The user terminal conducts receiving processes onassumption that the NR-PSS/SSS transmitted in the second cellcorresponds to SS block index # X. When the user terminal detects an SSblock (for example, NR-PSS/SSS) at a predetermined timing, the userterminal can recognize that the predetermined timing is the time indexcorresponding to SS block index # X.

If the second cell works in multi-beam operation, for example, the radiobase station reports the assist information to the user terminal to theeffect that the number of beams is N and that the active beams includebeam indices # X_₁ to X__(N). The user terminal performs receivingprocesses on assumption that the NR-PSS/SSS corresponding to SS blockindices # X_₁ to X__(N) are transmitted in the second cell. Also, theuser terminal may perform receiving processes on assumption that SSblock index-acquiring signals, corresponding to each NR-PSS/SSS, aretransmitted. Also, the user terminal may perform the detection processonly for a predetermined period based on the reported beam indices (orSS block indices).

The user terminal can identify a predetermined SS block index based on apredetermined synchronization signal (for example, NR-PSS/SSS) that isdetected, and an SS block index-acquiring signal (for example, a TSSand/or a second NR-PBCH). Each SS block may be comprised of anNR-PSS/SSS and a SS block index-acquiring signal.

In multi-beam operation, a predetermined number of beam indices (or SSblock indices) are reported to the user terminal in advance, so that therange of SS blocks the user terminal searches (detection period) can benarrowed down. Note that the beam indices to be reported to the userterminal may be contiguous or non-contiguous.

EXAMPLE 3

The radio base station may report ON/OFF of each beam index to the userterminal using a bitmap. For example, in single-beam operation, it isreported to the user terminal, by using a bitmap, that 1 beam is on. Forexample, in multi-beam operation, it is reported to the user terminal,by using a bitmap, that multiple beams are on.

When the second cell works in single-beam operation, it is reported tothe user terminal, by using a bitmap, that 1 beam index (for example,beam index # X) is on. The user terminal can identify the time index onassumption that an SS block detected in the second cell corresponds tobeam index # X reported based on the bitmap.

If the second cell works in multi-beam operation, for example, the radiobase station reports to the user terminal that the beams that are oninclude beam indices # X_₁ to X__(N), by using a bitmap. The userterminal performs receiving processes on assumption that the NR-PSS/SSScorresponding to SS block indices # X_₁ to X__(N) are transmitted in thesecond cell. Also, the user terminal may perform receiving processes onassumption that SS block index-acquiring signals, corresponding to eachNR-PSS/SSS, are transmitted. Also, the user terminal may perform thedetection process only for a predetermined period based on the reportedbeam indices (or SS block indices).

The user terminal can identify a predetermined SS block index based on apredetermined synchronization signal (for example, NR-PSS/SSS) that isdetected, and an SS block index-acquiring signal (for example, a TSSand/or a second NR-PBCH). Each SS block may be comprised of anNR-PSS/SSS and a SS block index-acquiring signal.

In multi-beam operation, a predetermined number of beam indices (or SSblock indices) are reported to the user terminal in advance, so that therange of SS blocks the user terminal searches (detection period) can benarrowed down. Note that the beam indices to be reported to the userterminal may be contiguous or non-contiguous.

Also, the number of bits required for the bitmap-reporting may be afixed value based on the maximum number of SS blocks per frequency band.

EXAMPLE 4

In addition to information about the synchronization (for example,whether or not SFN synchronization has been established) between thefirst cell and the second cell, the radio base station may reportinformation as to whether or not symbol synchronization is established(for example, symbol offset) and/or whether or not slot synchronizationis established (for example, slot offset). If the symbol offset is lessthan the predetermined value (for example, less than the number ofsymbols that form the slot), the user terminal can control thetransmitting and receiving processes on assumption that the slot timingin the second cell matches that of the first cell.

In addition, when symbol synchronization is established between thefirst cell and the second cell, the user terminal may perform processesfor connecting with the second cell without reading SS block indices inthe multi-beam operation.

(Variations of Examples)

The operation on the user terminal side when no synchronizationinformation is received (default operation) may be defined in advance.For example, when no synchronization information is received from thefirst cell, the user terminal controls the processes for connecting withthe second cell based on the assumption that the first cell and thesecond cell are not synchronized. For example, when no synchronizationinformation is received from the first cell, the user terminal controlsthe processes for connecting with the second cell based on theassumption that the first cell and the second cell are synchronized.

Also, the operation on the user terminal side when information about themode of operation in the second cell is not received (default operation)may be defined in advance. For example, when information about the beamoperation (including information about the number of beams) in thesecond cell is not received from the first cell, the user terminalcontrols the processes for connecting with the second cell on assumptionthat the second cell works in single-beam operation. Alternatively, wheninformation about the beam operation (including information about thenumber of beams) in the second cell is not received from the first cell,the user terminal controls the processes for connecting with the secondcell on assumption that the second cell works in multi-beam operation.

Also, the user terminal may measure the SFN offset between the firstcell and the second cell and report it to the radio base station. Inthis case, the user terminal may report to the radio base stationwhether or not the user terminal supports the UE capability formeasuring and/or reporting offsets between different cells. The radiobase station may configure offset measurement and/or reporting, byhigher layer signaling (or MAC signal), to a user terminal that supportsthe UE capability for measuring and/or reporting offsets betweendifferent cells. Also, a user terminal to support the UE capability formeasuring and/or reporting offsets between different cells may bedesigned to send reports to the radio base station when the SFN offsetvalue reported as synchronization information is different from the SFNoffset value measured at the user terminal. For example, when thedifference between the reported SFN value and the SFN value measured bythe user terminal is greater than or equal to a predetermined value, theuser terminal reports to that effect to the radio base station. Thus,regarding whether the user terminal sends a report or not, an eventtrigger using a predetermined value as a trigger condition may beconfigured. The predetermined value may be defined in advance by thespecification, or may be configured from the radio base station to theuser terminal. In this way, by reporting SFN offset information from theuser terminal to the radio base station, it is possible for the userterminal and the radio base station to share an understanding as towhether or not varying cells are synchronized (offset information).

(Radio Communication System)

Now, the structure of the radio communication system according to oneembodiment of the present invention will be described below. In thisradio communication system, communication is performed using one or acombination of the herein-contained embodiments of the presentinvention.

FIG. 9 is a diagram to show an exemplary schematic structure of a radiocommunication system according to one embodiment of the presentinvention. A radio communication system 1 can adopt carrier aggregation(CA) and/or dual connectivity (DC) to group a plurality of fundamentalfrequency blocks (component carriers) into one, where the LTE systembandwidth (for example, 20 MHz) constitutes 1 unit.

Note that the radio communication system 1 may be referred to as “LTE(Long Term Evolution),” “LTE-A (LTE-Advanced),” “LTE-B (LTE-Beyond),”“SUPER 3G, “IMT-Advanced,” “4G (4th generation mobile communicationsystem),” “5G (5th generation mobile communication system),” “FRA(Future Radio Access),” “New-RAT (Radio Access Technology)” and so on,or may be seen as a system to implement these.

The radio communication system 1 includes a radio base station 11 thatforms a macro cell C1, with a relatively wide coverage, and radio basestations 12 a to 12 c that are placed within the macro cell C1 and thatform small cells C2, which are narrower than the macro cell C1. Also,user terminals 20 are placed in the macro cell C1 and in each small cellC2.

The user terminals 20 can connect with both the radio base station 11and the radio base stations 12. The user terminals 20 may use the macrocell C1 and the small cells C2 at the same time by means of CA or DC.Furthermore, the user terminals 20 may apply CA or DC using a number ofcells (CCs) (for example, five or fewer CCs or six or more CCs). Forexample, in DC, the MeNB (MCG) communicates by using LTE cells, andSeNBs (SCGs) communicate by using NR/5G cells.

Between the user terminals 20 and the radio base station 11,communication can be carried out using a carrier of a relatively lowfrequency band (for example, 2 GHz) and a narrow bandwidth (referred toas, for example, an “existing carrier,” a “legacy carrier” and so on).Meanwhile, between the user terminals 20 and the radio base stations 12,a carrier of a relatively high frequency band (for example, 3.5 GHz, 5GHz and so on) and a wide bandwidth may be used, or the same carrier asthat used in the radio base station 11 may be used. Note that thestructure of the frequency band for use in each radio base station is byno means limited to these.

A structure may be employed here in which wire connection (for example,means in compliance with the CPRI (Common Public Radio Interface) suchas optical fiber, the X2 interface and so on) or wireless connection isestablished between the radio base station 11 and the radio base station12 (or between 2 radio base stations 12).

The radio base station 11 and the radio base stations 12 are eachconnected with higher station apparatus 30, and are connected with acore network 40 via the higher station apparatus 30. Note that thehigher station apparatus 30 may be, for example, access gatewayapparatus, a radio network controller (RNC), a mobility managemententity (MME) and so on, but is by no means limited to these. Also, eachradio base station 12 may be connected with the higher station apparatus30 via the radio base station 11.

Note that the radio base station 11 is a radio base station having arelatively wide coverage, and may be referred to as a “macro basestation,” a “central node,” an “eNB (eNodeB),” a “transmitting/receivingpoint” and so on. Also, the radio base stations 12 are radio basestations having local coverages, and may be referred to as “small basestations,” “micro base stations,” “pico base stations,” “femto basestations,” “HeNBs (Home eNodeBs),” “RRHs (Remote Radio Heads),”“transmitting/receiving points” and so on. Hereinafter the radio basestations 11 and 12 will be collectively referred to as “radio basestations 10,” unless specified otherwise.

The user terminals 20 are terminals to support various communicationschemes such as LTE, LTE-A and so on, and may be either mobilecommunication terminals (mobile stations) or stationary communicationterminals (fixed stations).

In the radio communication system 1, as radio access schemes, orthogonalfrequency division multiple access (OFDMA) is applied to the downlink,and single-carrier frequency division multiple access (SC-FDMA) isapplied to the uplink.

OFDMA is a multi-carrier communication scheme to perform communicationby dividing a frequency bandwidth into a plurality of narrow frequencybandwidths (subcarriers) and mapping data to each subcarrier. SC-FDMA isa single-carrier communication scheme to mitigate interference betweenterminals by dividing the system bandwidth into bands formed with one orcontinuous resource blocks per terminal, and allowing a plurality ofterminals to use mutually different bands. Note that the uplink anddownlink radio access schemes are not limited to this combination, andother radio access schemes may be used as well.

In the radio communication system 1, a downlink shared channel (PDSCH(Physical Downlink Shared CHannel)), which is used by each user terminal20 on a shared basis, a broadcast channel (PBCH (Physical BroadcastCHannel)), downlink L1/L2 control channels and so on are used asdownlink channels. User data, higher layer control information and SIBs(System Information Blocks) are communicated in the PDSCH. Also, the MIB(Master Information Block) is communicated in the PBCH. A shared controlchannel that reports the presence or absence of a paging channel ismapped to a downlink L1/L2 control channel (for example, PDCCH), and thepaging channel (PCH) data is mapped to the PDSCH. Downlink referencesignals, uplink reference signals and physical downlink synchronizationsignals are allocated separately.

The downlink L1/L2 control channels include a PDCCH (Physical DownlinkControl CHannel), an EPDCCH (Enhanced Physical Downlink ControlCHannel), a PCFICH (Physical Control Format Indicator CHannel), a PHICH(Physical Hybrid-ARQ Indicator CHannel) and so on. Downlink controlinformation (DCI), including PDSCH and PUSCH scheduling information, iscommunicated by the PDCCH. The number of OFDM symbols to use for thePDCCH is communicated by the PCFICH. HARQ (Hybrid Automatic RepeatreQuest) delivery acknowledgment information (also referred to as, forexample, “retransmission control information,” “HARQ-ACK,” “ACK/NACK,”etc.) in response to the PUSCH is transmitted by the PHICH. The EPDCCHis frequency-division-multiplexed with the PDSCH (downlink shared datachannel) and used to communicate DCI and so on, like the PDCCH.

In the radio communication system 1, an uplink shared channel (PUSCH(Physical Uplink Shared CHannel)), which is used by each user terminal20 on a shared basis, an uplink control channel (PUCCH (Physical UplinkControl CHannel)), a random access channel (PRACH (Physical RandomAccess CHannel)) and so on are used as uplink channels. User data,higher layer control information and so on are communicated in thePUSCH. Also, downlink radio quality information (CQI (Channel QualityIndicator)), delivery acknowledgement information and so on arecommunicated by the PUCCH. By means of the PRACH, random accesspreambles for establishing connections with cells are communicated.

In the radio communication system 1, cell-specific reference signals(CRSs), channel state information reference signals (CSI-RSs),demodulation reference signals (DMRSs), positioning reference signals(PRSs) and so on are communicated as downlink reference signals. Also,in the radio communication system 1, measurement reference signals (SRS(Sounding Reference Signal)), demodulation reference signal (DMRS) andso on are communicated as uplink reference signals. Note that the DMRSmay be referred to as a “user terminal-specific reference signal(UE-specific Reference Signal).” Also, the reference signals to becommunicated are by no means limited to these.

(Radio Base Station)

FIG. 10 is a diagram to show an exemplary overall structure of a radiobase station according to one embodiment of the present invention. Aradio base station 10 has a plurality of transmitting/receiving antennas101, amplifying sections 102, transmitting/receiving sections 103, abaseband signal processing section 104, a call processing section 105and a communication path interface 106. Note that one or moretransmitting/receiving antennas 101, amplifying sections 102 andtransmitting/receiving sections 103 may be provided.

User data to be transmitted from the radio base station 10 to a userterminal 20 on the downlink is input from the higher station apparatus30 to the baseband signal processing section 104, via the communicationpath interface 106.

In the baseband signal processing section 104, the user data issubjected to transmission processes, including a PDCP (Packet DataConvergence Protocol) layer process, user data division and coupling,RLC (Radio Link Control) layer transmission processes such as RLCretransmission control, MAC (Medium Access Control) retransmissioncontrol (for example, an HARQ (Hybrid Automatic Repeat reQuest)transmission process), scheduling, transport format selection, channelcoding, an inverse fast Fourier transform (IFFT) process and a precodingprocess, and the result is forwarded to each transmitting/receivingsection 103. Furthermore, downlink control signals are also subjected totransmission processes such as channel coding and an inverse fastFourier transform, and forwarded to each transmitting/receiving section103.

Baseband signals that are precoded and output from the baseband signalprocessing section 104 on a per antenna basis are converted into a radiofrequency band in the transmitting/receiving sections 103, and thentransmitted. The radio frequency signals having been subjected tofrequency conversion in the transmitting/receiving sections 103 areamplified in the amplifying sections 102, and transmitted from thetransmitting/receiving antennas 101. The transmitting/receiving sections103 can be constituted by transmitters/receivers, transmitting/receivingcircuits or transmitting/receiving apparatus that can be described basedon general understanding of the technical field to which the presentinvention pertains. Note that a transmitting/receiving section 103 maybe structured as a transmitting/receiving section in one entity, or maybe constituted by a transmitting section and a receiving section.

Meanwhile, as for uplink signals, radio frequency signals that arereceived in the transmitting/receiving antennas 101 are each amplifiedin the amplifying sections 102. The transmitting/receiving sections 103receive the uplink signals amplified in the amplifying sections 102. Thereceived signals are converted into the baseband signal throughfrequency conversion in the transmitting/receiving sections 103 andoutput to the baseband signal processing section 104.

In the baseband signal processing section 104, user data that isincluded in the uplink signals that are input is subjected to a fastFourier transform (FFT) process, an inverse discrete Fourier transform(IDFT) process, error correction decoding, a MAC retransmission controlreceiving process, and RLC layer and PDCP layer receiving processes, andforwarded to the higher station apparatus 30 via the communication pathinterface 106. The call processing section 105 performs call processingsuch as setting up and releasing communication channels, manages thestate of the radio base stations 10 and manages the radio resources.

The communication path interface section 106 transmits and receivessignals to and from the higher station apparatus 30 via a predeterminedinterface. Also, the communication path interface 106 may transmit andreceive signals (backhaul signaling) with other radio base stations 10via an inter-base station interface (which is, for example, opticalfiber that is in compliance with the CPRI (Common Public RadioInterface), the X2 interface, etc.).

Note that the transmitting/receiving sections 103 include an analog beamforming section that is configured to be able to adopt both multi-beamapproach and single-beam approach, and that provides analog beamforming. When a synchronization signal and/or a paging channel aretransmitted based on the multi-beam approach, beam sweeping is executed,whereby beams are switched (sweeping) every 1 symbol or multiplecontiguous symbols as 1 unit. The beamforming section may be constitutedby a beamforming circuit (for example, a phase shifter, a phase shiftingcircuit, etc.) or beamforming apparatus (for example, a phase shiftingdevice) that can be described based on general understanding of thetechnical field to which the present invention pertains. Furthermore,the transmitting/receiving antennas 101 may be constituted by, forexample, array antennas.

The transmitting/receiving sections 103 transmit a synchronizationsignal (NR-PSS/SSS), broadcast channel (NR-PBCH), system information(SIB), SS block, synchronization information, assist information and thelike. For example, the transmitting/receiving sections 103 transmitinformation about the mode of beams in a predetermined cell and/orinformation about the configuration of SS blocks (for example, theindices of synchronization signal blocks) as assist information.

FIG. 11 is a diagram to show an exemplary functional structure of aradio base station according to one embodiment of the present invention.Note that, although this example primarily shows functional blocks thatpertain to characteristic parts of the present embodiment, the radiobase station 10 has other functional blocks that are necessary for radiocommunication as well.

The baseband signal processing section 104 has a control section(scheduler) 301, a transmission signal generation section 302, a mappingsection 303, a received signal processing section 304 and a measurementsection 305. Note that these configurations have only to be included inthe radio base station 10, and some or all of these configurations maynot be included in the baseband signal processing section 104. Thebaseband signal processing section 104 has digital beamforming functionsfor providing digital beamforming.

The control section (scheduler) 301 controls the whole of the radio basestation 10. The control section 301 can be constituted by a controller,a control circuit or control apparatus that can be described based ongeneral understanding of the technical field to which the presentinvention pertains.

The control section 301 controls, for example, generation of signals inthe transmission signal generation section 302 (including signals thatcorrespond to synchronization signals, the MIB, paging channels, andbroadcast channels and so on), allocation of signals in the mappingsection 303, and so on.

The control section 301 controls scheduling of system information (SIBs,the MIB, etc.), downlink data signals that are transmitted in the PDSCH(including the PCH for paging messages), and downlink control signalsthat are transmitted in the PDCCH and/or the EPDCCH (covering, forexample, resource allocation, the shared control channel that reportswhether or not a paging message is present, the signal to report themulti-beam approach or the single-beam approach, and so on).

The transmission signal generation section 302 generates downlinksignals (downlink control signals, downlink data signals, downlinkreference signals and so on) based on commands from the control section301, and outputs these signals to the mapping section 303. Thetransmission signal generation section 302 can be constituted by asignal generator, a signal generating circuit or signal generatingapparatus that can be described based on general understanding of thetechnical field to which the present invention pertains.

For example, the transmission signal generation section 302 generates DLassignments, which report downlink signal allocation information, and ULgrants, which report uplink signal allocation information, based oncommands from the control section 301. Also, the downlink data signalsare subjected to the coding process, the modulation process and so on,by using coding rates and modulation schemes that are selected based on,for example, channel state information (CSI) from each user terminal 20.

The mapping section 303 maps the downlink signals generated in thetransmission signal generation section 302 to predetermined radioresources based on commands from the control section 301, and outputsthese to the transmitting/receiving sections 103. The mapping section303 can be constituted by a mapper, a mapping circuit or mappingapparatus that can be described based on general understanding of thetechnical field to which the present invention pertains.

The received signal processing section 304 performs receiving processes(for example, demapping, demodulation, decoding and so on) of receivedsignals that are input from the transmitting/receiving sections 103.Here, the received signals include, for example, uplink signalstransmitted from the user terminal 20 (uplink control signals, uplinkdata signals, uplink reference signals, etc.). For the received signalprocessing section 304, a signal processor, a signal processing circuitor signal processing apparatus that can be described based on generalunderstanding of the technical field to which the present inventionpertains can be used.

The received signal processing section 304 outputs the decodedinformation, acquired through the receiving processes, to the controlsection 301. For example, when a PUCCH to contain an HARQ-ACK isreceived, the received signal processing section 304 outputs thisHARQ-ACK to the control section 301. FIG. 11 is a diagram to show anexemplary functional structure of a radio base station according to oneembodiment of the present invention.

The measurement section 305 conducts measurements with respect to thereceived signal. The measurement section 305 can be constituted by ameasurer, a measurement circuit or measurement apparatus that can bedescribed based on general understanding of the technical field to whichthe present invention pertains.

The measurement section 305 may measure, for example, the received power(for example, RSRP (Reference Signal Received Power)), the receivedquality (for example, RSRQ (Reference Signal Received Quality)), theSINR (Signal to Interference plus Noise Ratio), channel states and so onof the received signals. The measurement results may be output to thecontrol section 301.

(User Terminal)

FIG. 12 is a diagram to show an exemplary overall structure of a userterminal according to one embodiment of the present invention. A userterminal 20 has a plurality of transmitting/receiving antennas 201,amplifying sections 202, transmitting/receiving sections 203, a basebandsignal processing section 204 and an application section 205. Note thatone or more transmitting/receiving antennas 201, amplifying sections 202and transmitting/receiving sections 203 may be provided.

Radio frequency signals that are received in the transmitting/receivingantennas 201 are amplified in the amplifying sections 202. Thetransmitting/receiving sections 203 receive the downlink signalsamplified in the amplifying sections 202. The received signals aresubjected to frequency conversion and converted into the baseband signalin the transmitting/receiving sections 203, and output to the basebandsignal processing section 204. A transmitting/receiving section 203 canbe constituted by a transmitters/receiver, a transmitting/receivingcircuit or transmitting/receiving apparatus that can be described basedon general understanding of the technical field to which the presentinvention pertains. Note that a transmitting/receiving section 203 maybe structured as a transmitting/receiving section in one entity, or maybe constituted by a transmitting section and a receiving section.

The baseband signal processing section 204 performs, for the basebandsignal that is input, an FFT process, error correction decoding, aretransmission control receiving process and so on. Downlink user datais forwarded to the application section 205. The application section 205performs processes related to higher layers above the physical layer andthe MAC layer, and so on. Furthermore, in the downlink data, broadcastinformation is also forwarded to the application section 205.

Meanwhile, uplink user data is input from the application section 205 tothe baseband signal processing section 204. The baseband signalprocessing section 204 performs a retransmission control transmissionprocess (for example, an HARQ transmission process), channel coding,precoding, a discrete Fourier transform (DFT) process, an IFFT processand so on, and the result is forwarded to the transmitting/receivingsections 203. Baseband signals that are output from the baseband signalprocessing section 204 are converted into a radio frequency band in thetransmitting/receiving sections 203 and transmitted. The radio frequencysignals that are subjected to frequency conversion in thetransmitting/receiving sections 203 are amplified in the amplifyingsections 202, and transmitted from the transmitting/receiving antennas201.

Note that the transmitting/receiving sections 203 may furthermore havean analog beamforming section that forms analog beams. The analogbeamforming section may be constituted by an analog beamforming circuit(for example, a phase shifter, a phase shifting circuit, etc.) or analogbeamforming apparatus (for example, a phase shifting device) that can bedescribed based on general understanding of the technical field to whichthe present invention pertains. Furthermore, the transmitting/receivingantennas 201 may be constituted by, for example, array antennas.

The transmitting/receiving sections 203 transmit a synchronizationsignal (NR-PSS/SSS), broadcast channel (NR-PBCH), system information(SIB), SS block, synchronization information, assist information and thelike. For example, the transmitting/receiving sections 203 transmitinformation about the mode of beams in a predetermined cell and/orinformation about the configuration of SS blocks (for example, theindices of synchronization signal blocks) as assist information.

FIG. 13 is a diagram to show an exemplary functional structure of a userterminal according to one embodiment of the present invention. Notethat, although this example primarily shows functional blocks thatpertain to characteristic parts of the present embodiment, the userterminal 20 has other functional blocks that are necessary for radiocommunication as well.

The baseband signal processing section 204 provided in the user terminal20 at least has a control section 401, a transmission signal generationsection 402, a mapping section 403, a received signal processing section404 and a measurement section 405. Note that these configurations haveonly to be included in the user terminal 20, and some or all of theseconfigurations may not be included in the baseband signal processingsection 204.

The control section 401 controls the whole of the user terminal 20. Forthe control section 401, a controller, a control circuit or controlapparatus that can be described based on general understanding of thetechnical field to which the present invention pertains can be used.

The control section 401 controls, for example, generation of signals inthe transmission signal generation section 402, allocation of signals inthe mapping section 403, and so on. Furthermore, the control section 401controls signal receiving processes in the received signal processingsection 404, measurements of signals in the measurement section 405, andso on.

The control section 401 controls the processes for connecting with apredetermined cell (for example, PSCell) based on information aboutsynchronization and/or information about the configuration ofsynchronization signal blocks. For example, the control section 401controls whether or not to receive a broadcast channel transmitted froma predetermined cell based on information about synchronization and/orinformation about the configuration of synchronization signal blocks.

Also, when information to indicate that the first cell and the secondcell are synchronized or information to indicate that the time offsetbetween the first cell and the second cell is equal to or less than apredetermined value is received, the control section 401 judges that thesystem frame number of the first cell and the system frame number of thesecond cell are the same.

The transmission signal generation section 402 generates uplink signals(uplink control signals, uplink data signals, uplink reference signals,etc.) based on commands from the control section 401, and outputs thesesignals to the mapping section 403. The transmission signal generationsection 402 can be constituted by a signal generator, a signalgenerating circuit or signal generating apparatus that can be describedbased on general understanding of the technical field to which thepresent invention pertains.

For example, the transmission signal generation section 402 generatesuplink control signals related to delivery acknowledgement informationand/or channel state information (CSI) based on commands from thecontrol section 401. Also, the transmission signal generation section402 generates uplink data signals based on commands from the controlsection 401. For example, when a UL grant is included in a downlinkcontrol signal that is reported from the radio base station 10, thecontrol section 401 commands the transmission signal generation section402 to generate an uplink data signal.

The mapping section 403 maps the uplink signals generated in thetransmission signal generation section 402 to radio resources based oncommands from the control section 401, and outputs the result to thetransmitting/receiving sections 203. The mapping section 403 can beconstituted by a mapper, a mapping circuit or mapping apparatus that canbe described based on general understanding of the technical field towhich the present invention pertains.

The received signal processing section 404 performs receiving processes(for example, demapping, demodulation, decoding and so on) of receivedsignals that are input from the transmitting/receiving sections 203.Here, the received signals include, for example, downlink signals(downlink control signals, downlink data signals, downlink referencesignals and so on) that are transmitted from the radio base station 10.The received signal processing section 404 can be constituted by asignal processor, a signal processing circuit or signal processingapparatus that can be described based on general understanding of thetechnical field to which the present invention pertains. Also, thereceived signal processing section 404 can constitute the receivingsection according to the present invention.

As commanded by the control section 401, the received signal processingsection 404 receives synchronization signals and broadcast channels,which the radio base station transmits by applying beamforming. Inparticular, the received signal processing section 404 receives thesynchronization signal and broadcast channel that are allocated to atleast one of a plurality of time fields (for example, symbols) thatconstitute a predetermined transmission time interval (for example, asubframe or a slot).

The received signal processing section 404 outputs the decodedinformation, acquired through the receiving processes, to the controlsection 401. The received signal processing section 404 outputs, forexample, broadcast information, system information, RRC signaling, DCIand so on, to the control section 401. Also, the received signalprocessing section 404 outputs the received signals, the signals afterthe receiving processes and so on, to the measurement section 405.

The measurement section 405 conducts measurements with respect to thereceived signals. For example, the measurement section 405 conductsmeasurements using beamforming RSs transmitted from the radio basestation 10. The measurement section 405 can be constituted by ameasurer, a measurement circuit or measurement apparatus that can bedescribed based on general understanding of the technical field to whichthe present invention pertains.

The measurement section 405 may measure, for example, the received power(for example, RSRP), the received quality (for example, RSRQ, receivedSINR, etc.), channel states and so on of the received signals. Themeasurement results may be output to the control section 401.

(Hardware Structure)

Note that the block diagrams that have been used to describe the aboveembodiments show blocks in functional units. These functional blocks(components) may be implemented in arbitrary combinations of hardwareand/or software. Also, the means for implementing each functional blockis not particularly limited. That is, each functional block may berealized by one piece of apparatus that is physically and/or logicallyaggregated, or may be realized by directly and/or indirectly connectingtwo or more physically and/or logically separate pieces of apparatus(via wire and/or wireless, for example) and using these multiple piecesof apparatus.

For example, the radio base station, user terminals and so on accordingto one embodiment of the present invention may function as a computerthat executes the processes of the radio communication method of thepresent invention. FIG. 14 is a diagram to show an exemplary hardwarestructure of a radio base station and a user terminal according to oneembodiment of the present invention. Physically, the above-describedradio base stations 10 and user terminals 20 may be formed as a computerapparatus that includes a processor 1001, a memory 1002, a storage 1003,communication apparatus 1004, input apparatus 1005, output apparatus1006 and a bus 1007.

Note that, in the following description, the word “apparatus” may bereplaced by “circuit,” “device,” “unit” and so on. Note that thehardware structure of a radio base station 10 and a user terminal 20 maybe designed to include one or more of each apparatus shown in thedrawings, or may be designed not to include part of the apparatus.

For example, although only 1 processor 1001 is shown, a plurality ofprocessors may be provided. Furthermore, processes may be implementedwith 1 processor, or processes may be implemented in sequence, or indifferent manners, on one or more processors. Note that the processor1001 may be implemented with one or more chips.

The functions of the radio base station 10 and the user terminal 20 areimplemented by allowing hardware such as the processor 1001 and thememory 1002 to read predetermined software (programs), thereby allowingthe processor 1001 to do calculations, the communication apparatus 1004to communicate, and the memory 1002 and the storage 1003 to read and/orwrite data.

The processor 1001 may control the whole computer by, for example,running an operating system. The processor 1001 may be configured with acentral processing unit (CPU), which includes interfaces with peripheralapparatus, control apparatus, computing apparatus, a register and so on.For example, the above-described baseband signal processing section 104(204), call processing section 105 and others may be implemented by theprocessor 1001.

Furthermore, the processor 1001 reads programs (program codes), softwaremodules, data and so forth from the storage 1003 and/or thecommunication apparatus 1004, into the memory 1002, and executes variousprocesses according to these. As for the programs, programs to allowcomputers to execute at least part of the operations of theabove-described embodiments may be used. For example, the controlsection 401 of the user terminals 20 may be implemented by controlprograms that are stored in the memory 1002 and that operate on theprocessor 1001, and other functional blocks may be implemented likewise.

The memory 1002 is a computer-readable recording medium, and may beconstituted by, for example, at least one of a ROM (Read Only Memory),an EPROM (Erasable Programmable ROM), an EEPROM (Electrically EPROM), aRAM (Random Access Memory) and/or other appropriate storage media. Thememory 1002 may be referred to as a “register,” a “cache,” a “mainmemory (primary storage apparatus)” and so on. The memory 1002 can storeexecutable programs (program codes), software modules and so on forimplementing the radio communication methods according to embodiments ofthe present invention.

The storage 1003 is a computer-readable recording medium, and may beconstituted by, for example, at least one of a flexible disk, a floppy(registered trademark) disk, a magneto-optical disk (for example, acompact disc (CD-ROM (Compact Disc ROM) and so on), a digital versatiledisc, a Blu-ray (registered trademark) disk), a removable disk, a harddisk drive, a smart card, a flash memory device (for example, a card, astick, a key drive, etc.), a magnetic stripe, a database, a server,and/or other appropriate storage media. The storage 1003 may be referredto as “secondary storage apparatus.”

The communication apparatus 1004 is hardware (transmitting/receivingdevice) for allowing inter-computer communication by using wired and/orwireless networks, and may be referred to as, for example, a “networkdevice,” a “network controller,” a “network card,” a “communicationmodule” and so on. The communication apparatus 1004 may be configured toinclude a high frequency switch, a duplexer, a filter, a frequencysynthesizer and so on in order to realize, for example, frequencydivision duplex (FDD) and/or time division duplex (TDD). For example,the above-described transmitting/receiving antennas 101 (201),amplifying sections 102 (202), transmitting/receiving sections 103(203), communication path interface 106 and so on may be implemented bythe communication apparatus 1004.

The input apparatus 1005 is an input device for receiving input from theoutside (for example, a keyboard, a mouse, a microphone, a switch, abutton, a sensor and so on). The output apparatus 1006 is an outputdevice for allowing sending output to the outside (for example, adisplay, a speaker, an LED (Light Emitting Diode) lamp and so on). Notethat the input apparatus 1005 and the output apparatus 1006 may beprovided in an integrated structure (for example, a touch panel).

Furthermore, these types of apparatus, including the processor 1001, thememory 1002 and others, are connected by a bus 1007 for communicatinginformation. The bus 1007 may be formed with a single bus, or may beformed with buses that vary between pieces of apparatus.

Also, the radio base station 10 and the user terminal 20 may bestructured to include hardware such as a microprocessor, a digitalsignal processor (DSP), an ASIC (Application-Specific IntegratedCircuit), a PLD (Programmable Logic Device), an FPGA (Field ProgrammableGate Array) and so on, and part or all of the functional blocks may beimplemented by the hardware. For example, the processor 1001 may beimplemented with at least one of these pieces of hardware.

(Variations)

Note that the terminology used in this specification and the terminologythat is needed to understand this specification may be replaced by otherterms that convey the same or similar meanings. For example, “channels”and/or “symbols” may be replaced by “signals” (or “signaling”). Also,“signals” may be “messages.” A reference signal may be abbreviated as an“RS,” and may be referred to as a “pilot,” a “pilot signal” and so on,depending on which standard applies. Furthermore, a “component carrier(CC)” may be referred to as a “cell,” a “frequency carrier,” a “carrierfrequency” and so on.

Furthermore, a radio frame may be comprised of one or more periods(frames) in the time domain. Each of one or more periods (frames)constituting a radio frame may be referred to as a “subframe.”Furthermore, a subframe may be comprised of one or more slots in thetime domain. Furthermore, a slot may be comprised of one or more symbolsin the time domain (OFDM (Orthogonal Frequency Division Multiplexing)symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access)symbols, and so on).

A radio frame, a subframe, a slot and a symbol all represent the timeunit in signal communication. A radio frame, a subframe, a slot and asymbol may be each called by other applicable names. For example, 1subframe may be referred to as a “transmission time interval (TTI),” aplurality of consecutive subframes may be referred to as a “TTI,” or 1slot may be referred to as a “TTI.” That is, a subframe and a TTI may bea subframe (1 ms) in existing LTE, may be a shorter period than 1 ms(for example, 1 to 13 symbols), or may be a longer period of time than 1ms.

Here, a TTI refers to the minimum time unit of scheduling in radiocommunication, for example. For example, in LTE systems, a radio basestation schedules the radio resources (such as the frequency bandwidthand transmission power that can be used in each user terminal) toallocate to each user terminal in TTI units. Note that the definition ofTTIs is not limited to this. TTIs may be transmission time units forchannel-encoded data packets (transport blocks), or may be the unit ofprocessing in scheduling, link adaptation and so on.

A TTI having a time duration of 1 ms may be referred to as a “normal TTI(TTI in LTE Rel. 8 to 12),” a “long TTI,” a “normal subframe,” a “longsubframe,” and so on. A TTI that is shorter than a normal TTI may bereferred to as a “shortened TTI,” a “short TTI,” a “shortened subframe,”a “short subframe,” and so on.

A resource block (RB) is the unit of resource allocation in the timedomain and the frequency domain, and may include one or a plurality ofconsecutive subcarriers in the frequency domain. Also, an RB may includeone or more symbols in the time domain, and may be 1 slot, 1 subframe or1 TTI in length. 1 TTI and 1 subframe each may be comprised of one ormore resource blocks. Note that an RB may be referred to as a “physicalresource block (PRB (Physical RB)),” a “PRB pair,” an “RB pair,” and soon.

Furthermore, a resource block may be comprised of one or more resourceelements (REs). For example, 1 RE may be a radio resource field of 1subcarrier and 1 symbol.

Note that the above-described structures of radio frames, subframes,slots, symbols and so on are merely examples. For example,configurations such as the number of subframes included in a radioframe, the number of slots included in a subframe, the number of symbolsand RBs included in a slot, the number of subcarriers included in an RB,the number of symbols in a TTI, the symbol duration and the cyclicprefix (CP) duration can be variously changed.

Also, the information and parameters described in this specification maybe represented in absolute values or in relative values with respect topredetermined values, or may be represented in other informationformats. For example, radio resources may be specified by predeterminedindices. In addition, equations to use these parameters and so on may beused, apart from those explicitly disclosed in this specification.

The names used for parameters and so on in this specification are in norespect limiting. For example, since various channels (PUCCH (PhysicalUplink Control CHannel), PDCCH (Physical Downlink Control CHannel) andso on) and information elements can be identified by any suitable names,the various names assigned to these individual channels and informationelements are in no respect limiting.

The information, signals and/or others described in this specificationmay be represented by using a variety of different technologies. Forexample, data, instructions, commands, information, signals, bits,symbols and chips, all of which may be referenced throughout theherein-contained description, may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orphotons, or any combination of these.

Also, information, signals and so on can be output from higher layers tolower layers and/or from lower layers to higher layers. Information,signals and so on may be input and/or output via a plurality of networknodes.

The information, signals and so on that are input and/or output may bestored in a specific location (for example, a memory), or may be managedusing a management table. The information, signals and so on to be inputand/or output can be overwritten, updated or appended. The information,signals and so on that are output may be deleted. The information,signals and so on that are input may be transmitted to other pieces ofapparatus.

Reporting of information is by no means limited to theexamples/embodiments described in this specification, and other methodsmay be used as well. For example, reporting of information may beimplemented by using physical layer signaling (for example, downlinkcontrol information (DCI), uplink control information (UCI), higherlayer signaling (for example, RRC (Radio Resource Control) signaling,broadcast information (the master information block (MIB), systeminformation blocks (SIBs) and so on), MAC (Medium Access Control)signaling and so on), and other signals and/or combinations of these.

Note that physical layer signaling may be referred to as “L1/L2 (Layer1/Layer 2) control information (L1/L2 control signals),” “L1 controlinformation (L1 control signal)” and so on. Also, RRC signaling may bereferred to as “RRC messages,” and can be, for example, an RRCconnection setup message, RRC connection reconfiguration message, and soon. Also, MAC signaling may be reported using, for example, MAC controlelements (MAC CEs (Control Elements)).

Also, reporting of predetermined information (for example, reporting ofinformation to the effect that “X holds”) does not necessarily have tobe sent explicitly, and can be sent implicitly (by, for example, notreporting this piece of information, or by reporting a different pieceof information).

Decisions may be made in values represented by 1 bit (0 or 1), may bemade in Boolean values that represent true or false, or may be made bycomparing numerical values (for example, comparison against apredetermined value).

Software, whether referred to as “software,” “firmware,” “middleware,”“microcode” or “hardware description language,” or called by othernames, should be interpreted broadly, to mean instructions, instructionsets, code, code segments, program codes, programs, subprograms,software modules, applications, software applications, softwarepackages, routines, subroutines, objects, executable files, executionthreads, procedures, functions and so on.

Also, software, commands, information and so on may be transmitted andreceived via communication media. For example, when software istransmitted from a website, a server or other remote sources by usingwired technologies (coaxial cables, optical fiber cables, twisted-paircables, digital subscriber lines (DSL) and so on) and/or wirelesstechnologies (infrared radiation, microwaves and so on), these wiredtechnologies and/or wireless technologies are also included in thedefinition of communication media.

The terms “system” and “network” as used herein are usedinterchangeably.

As used herein, the terms “base station (BS),” “radio base station,”“eNB,” “cell,” “sector,” “cell group,” “carrier,” and “componentcarrier” may be used interchangeably. A base station may be referred toas a “fixed station,” “NodeB,” “eNodeB (eNB),” “access point,”“transmission point,” “receiving point,” “femto cell,” “small cell” andso on.

A base station can accommodate one or more (for example, 3) cells (alsoreferred to as “sectors”). When a base station accommodates a pluralityof cells, the entire coverage area of the base station can bepartitioned into multiple smaller areas, and each smaller area canprovide communication services through base station subsystems (forexample, indoor small base stations (RRHs (Remote Radio Heads))). Theterm “cell” or “sector” refers to part or all of the coverage area of abase station and/or a base station subsystem that provides communicationservices within this coverage.

As used herein, the terms “mobile station (MS)” “user terminal,” “userequipment (UE)” and “terminal” may be used interchangeably. A basestation may be referred to as a “fixed station,” “NodeB,” “eNodeB(eNB),” “access point,” “transmission point,” “receiving point,” “femtocell,” “small cell” and so on.

A mobile station may also be referred to as, for example, a “subscriberstation,” a “mobile unit,” a “subscriber unit,” a “wireless unit,” a“remote unit,” a “mobile device,” a “wireless device,” a “wirelesscommunication device,” a “remote device,” a “mobile subscriber station,”an “access terminal,” a “mobile terminal,” a “wireless terminal,” a“remote terminal,” a “handset,” a “user agent,” a “mobile client,” a“client” or some other suitable terms.

Furthermore, the radio base stations in this specification may beinterpreted as user terminals. For example, each aspect/embodiment ofthe present invention may be applied to a configuration in whichcommunication between a radio base station and a user terminal isreplaced with communication among a plurality of user terminals (D2D(Device-to-Device)). In this case, user terminals 20 may have thefunctions of the radio base stations 10 described above. In addition,terms such as “uplink” and “downlink” may be interpreted as “side.” Forexample, an uplink channel may be interpreted as a side channel.

Likewise, the user terminals in this specification may be interpreted asradio base stations. In this case, the radio base stations 10 may havethe functions of the user terminals 20 described above.

Certain actions which have been described in this specification to beperformed by base stations may, in some cases, be performed by highernodes (upper nodes). In a network comprised of one or more network nodeswith base stations, it is clear that various operations that areperformed to communicate with terminals can be performed by basestations, one or more network nodes (for example, MMEs (MobilityManagement Entities), S-GW (Serving-Gateways), and so on may bepossible, but these are not limiting) other than base stations, orcombinations of these.

The examples/embodiments illustrated in this specification may be usedindividually or in combinations, which may be switched depending on themode of implementation. The order of processes, sequences, flowchartsand so on that have been used to describe the examples/embodimentsherein may be re-ordered as long as inconsistencies do not arise. Forexample, although various methods have been illustrated in thisspecification with various components of steps in exemplary orders, thespecific orders that are illustrated herein are by no means limiting.

The aspects/embodiments illustrated in this specification may be appliedto systems that use LTE (Long Term Evolution), LTE-A (LTE-Advanced),LTE-B (LTE-Beyond), SUPER 3G, IMT-Advanced, 4G (4th generation mobilecommunication system), 5G (5th generation mobile communication system),FRA (Future Radio Access), New-RAT (Radio Access Technology), NR(NewRadio), NX (New radio access), FX (Future generation radio access), GSM(registered trademark) (Global System for Mobile communications), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registeredtrademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20,UWB (Ultra-WideBand), Bluetooth (registered trademark) and otheradequate radio communication methods, and/or next-generation systemsthat are enhanced based on these.

The phrase “based on” as used in this specification does not mean “basedonly on,” unless otherwise specified. In other words, the phrase “basedon” means both “based only on” and “based at least on.”

Reference to elements with designations such as “first,” “second” and soon as used herein does not generally limit the number/quantity or orderof these elements. These designations are used herein only forconvenience, as a method of distinguishing between two or more elements.In this way, reference to the first and second elements does not implythat only 2 elements may be employed, or that the first element mustprecede the second element in some way.

The terms “judge” and “determine” as used herein may encompass a widevariety of actions. For example, to “judge” and “determine” as usedherein may be interpreted to mean making judgements and determinationsrelated to calculating, computing, processing, deriving, investigating,looking up (for example, searching a table, a database or some otherdata structure), ascertaining and so on. Furthermore, to “judge” and“determine” as used herein may be interpreted to mean making judgementsand determinations related to receiving (for example, receivinginformation), transmitting (for example, transmitting information),inputting, outputting, accessing (for example, accessing data in amemory) and so on. In addition, to “judge” and “determine” as usedherein may be interpreted to mean making judgements and determinationsrelated to resolving, selecting, choosing, establishing, comparing andso on. In other words, to “judge” and “determine” as used herein may beinterpreted to mean making judgements and determinations related to someaction.

As used herein, the terms “connected” and “coupled,” or any variation ofthese terms, mean all direct or indirect connections or coupling betweentwo or more elements, and may include the presence of one or moreintermediate elements between 2 elements that are “connected” or“coupled” to each other. The coupling or connection between the elementsmay be physical, logical or a combination thereof. As used herein, 2elements may be considered “connected” or “coupled” to each other byusing one or more electrical wires, cables and/or printed electricalconnections, and, as a number of non-limiting and non-inclusiveexamples, by using electromagnetic energy, such as electromagneticenergy having wavelengths in radio frequency fields, microwave regionsand optical (both visible and invisible) regions.

When terms such as “include,” “comprise” and variations of these areused in this specification or in claims, these terms are intended to beinclusive, in a manner similar to the way the term “provide” is used.Furthermore, the term “or” as used in this specification or in claims isintended to be not an exclusive disjunction.

Now, although the present invention has been described in detail above,it should be obvious to a person skilled in the art that the presentinvention is by no means limited to the embodiments described herein.The present invention can be implemented with various corrections and invarious modifications, without departing from the spirit and scope ofthe present invention defined by the recitations of claims.Consequently, the description herein is provided only for the purpose ofexplaining examples, and should by no means be construed to limit thepresent invention in any way.

The invention claimed is:
 1. A terminal comprising: a receiver thatreceives information related to a synchronization signal block indexindicated by using a bitmap, by higher layer signaling; and a controllerthat controls a reception of a synchronization signal block based on theinformation related to the synchronization signal block index.
 2. Theterminal according to claim 1, wherein the information related to thesynchronization signal block index comprises information notified byusing the bitmap, related to whether or not a plurality ofsynchronization signal block indexes is transmitted.
 3. The terminalaccording to claim 2, wherein a number of bits needed for transmittingthe information that is notified by the bitmap is determined based on amaximum number of synchronization signal blocks per frequency band. 4.The terminal according to claim 3, wherein each synchronization signalblock index corresponds to a separate time index.
 5. The terminalaccording to claim 2, wherein each synchronization signal block indexcorresponds to a separate time index.
 6. The terminal according to claim1, wherein each synchronization signal block index corresponds to aseparate time index.
 7. A radio communication method comprising:receiving information related to a synchronization signal block indexindicated by using a bitmap, by higher layer signaling; and controllingreception of a synchronization signal block based on the informationrelated to the synchronization signal block index.
 8. A base stationcomprising: a transmitter that transmits information related to asynchronization signal block index indicated by using a bitmap, byhigher layer signaling; and a controller that controls a transmission ofa synchronization signal block based on the information related to thesynchronization signal block index.
 9. A system comprising a terminaland a base station, wherein: the terminal comprises: a receiver thatreceives information related to a synchronization signal block indexindicated by using a bitmap, by higher layer signaling; and a firstcontroller that controls a reception of a synchronization signal blockbased on the information related to the synchronization signal blockindex; and the base station comprises: a transmitter that transmits theinformation related to the synchronization signal block index by higherlayer signaling; and a second controller that controls a transmission ofthe synchronization signal block based on the information related to thesynchronization signal block index.